X-ray crystallography and small-angle x-ray scattering (SAXS) are powerful methods for studying biological assemblies and conformational changes in macromolecules that provide information complementary to high-resolution X-ray crystallography and NMR. The Johns Hopkins University has a large group (16 PIs) of NIH-funded investigators in the Schools of Medicine, Public Health, and Arts and Sciences that utilize SAXS and X-ray crystallography to study a range of problems central to the NIH mission. The requested in-house SAXS system will benefit ongoing projects that utilize SAXS while opening the door to studying systems involving macromolecules and complexes that deteriorate and aggregate over time and thus do not survive shipping to synchrotron beamlines for SAXS data collection. The system requested takes advantage of an existing high-brilliance generator housed at the School of Medicine to obtain in-house SAXS data of optimal quality. To maintain high throughput for in-house single- crystal X-ray diffraction data collection, and since we plan t utilize one of two generator ports for SAXS, we also are requesting a Pilatus pixel-array detector to replace the existing image- plate and CCD detectors currently mounted on both ports. In addition to shortening data collection times, a Pilatus detector offers the added benefit of enabling screening of smaller crystals and collecting higher resolution data sets for structure determination efforts. All of the requested equipment will be incorporated into an X-ray diffraction facility that has served as a core facility for over two decades and is staffed by an experienced PhD-level crystallographer. The University has made a substantial financial commitment to this facility and its upgrade, including providing full salary support for the X-ray lab manager, prepared laboratory space, matching funds, and a guarantee of ongoing financial support to cover service contracts and repairs. The equipment will have an immediate and lasting impact on a broad range of areas including cancer biology, DNA replication, ribosome assembly, intracellular signaling, transcriptional regulation, genomic integrity, neuronal function and multidrug resistance.